Most transisterized power supplies utilize silicon controlled rectifiers (SCR) switching in the alternating current (AC) line or a transistor as a series element to attain regulation. The SCR method requires the use of phase controls synchronous to the AC line to allow only the desired portion of the AC signal to pass. Because of this, fast rise times are experienced causing large transients in the output, also phasing controls can become quite complex. SCR's also have a forward voltage drop between 1.5 volts in low current devices to 3 volts in high current devices. The use of a series element usually has high power dissapation and limited range.